1. Field of the Invention
The present invention relates to multiple-tuner receiver systems and specifically to distribution of multiple received signals to multiple tuners.
2. Prior Art
FIG. 1 shows an application requiring the distribution and processing of multiple signals in a direct broadcast satellite (DBS) receiver system where there are multiple low noise block converters (LNBs) that receive signals from multiple satellite transmitters. Additionally, each satellite signal may have a horizontal and vertical polarized signal that results in two output signals from each LNB. For a three LNB receiver antenna, there could be six independent bands of signals that require distribution to satellite integrated receiver decoders (IRDs). Any IRD may attempt to tune any one of the bands, requiring an N-way crosspoint connection from any LNB output to any IRD. Conventional satellite outdoor units (ODUs) use a multiport switch to route an LNB signal to an IRD that is controlled by signals from the IRDs transmitted up the coaxial cable connection to the ODU.
Multiple-tuner receivers are used in IRDs, cable set-top boxes (STBs), and picture-in-picture (PIP) television receivers when more than one television signal requires simultaneous processing. Digital video recorders (DVRs) also use multiple tuners to record one or more channels while another channel is being displayed.
The tuners each receive a radio frequency (RF) signal comprising several frequency division multiplexed (FDM) channels. The tuners select one channel for processing. The tuner may comprise the functions of bandpass filtering and frequency translation.
As shown in FIG. 2, conventional multiple tuner receiver systems receive one or more broadband signals comprising many independent channels and power split each broadband signal, with or without amplification, to drive multiple tuners. A power splitter is typically a passive device and can function as a summer or a splitter. The power splitting and amplification results in a degradation of the signal to noise ratio (SNR) of the signal.
When using a two-layer circuit board, splitting and distributing signals to multiple devices is difficult due to the need for signal crossovers, disruption of the ground plane, and switching between layers. These routing issues in the circuit board wiring disturb the controlled impedance of the wiring and alter the power level balance across the broadband signal and among the various signals. A further problem is implementing splitters on a circuit board for signal frequencies below standard satellite intermediate frequencies, which is challenging due to the long wavelengths and large circuit element sizes.